Solubilization and purification of surface antigen of cells transformed by adenovirus type 12

Isolation of immunogenic and suppressogenic glycoproteins from adenovirus type 12 hamster tumor cells

Two types of glycoproteins were isolated from the membrane fraction of adenovirus type 12 (Ad12) hamster tumor cells by recovering detergent-solubilized glycoproteins using concanavalin A-affinity chromatography and gel filtration. One of the glycoproteins consisted of a polypeptide of 130,000 daltons (130K) with a pI value of 4.7-5.1, and the other consisted of a polypeptide of 18,500 daltons (18.5K) with a pI value of 6.3-6.6. The glycoproteins were immunologically different. The 18.5K glycoprotein induced in vivo resistance to tumor growth and anti-tumor cytotoxic T cells, while the 130K glycoprotein induced in vivo suppressor T cells which inhibited the activity of anti-tumor cytotoxic T cells.

Adenovirus type 12 specific cell surface antigen in transformed cells is a product of the E1b early region

Six syngeneic rat cell lines transformed with isolated or cloned left end fragments of adenovirus type 12 (Ad12) DNA were used in a study of the Ad12-specific cell surface antigen. Cells transformed with EcoRI-C, SalI-C, and HindIII-G fragments of Ad12 DNA fragment-transformed express the E1a and a part of or a complete E1b early regions. Two AccI-H DNA fragment-transformed cell lines contain and express only the E1a region. All these cells contain nuclear Ad12 antigen. Cytotoxic antibodies raised against syngeneic EcoRI-C DNA fragment-transformed cells kill EcoRI-C, SalI-C and HindIII-G fragment-transformed cells, but fail to kill cells transformed with AccI-H DNA fragment. Immunofluorescence analysis shows that such antibodies, which stain the surface of cells expressing the E1b region, do not stain the surface of AccI-H DNA fragment-transformed cells. Cells transformed with AccI-H fragment are also not killed by secondary cytolytic T cells, raised and effective against cells transformed with EcoRI-C, SalI-C, and HindIII-G DNA fragments. Cells transformed with AccI-H fragment do not elicit cytolytic T cells against any of the studied cell lines. The only Ad12-specific product shared by all cell lines killed in cytolytic assays which is absent from AccI-H fragment-transformed cells is the E1b 18K protein. Since it has also been shown in other studies that this protein is associated with the cellular membrane, the simplest interpretation of these data is that the Ad12-specific cell surface antigen in transformed rat cells is a product of the left end of the E1b region.

Comparative study by immunofluorescence of T and P antigens induced by adenovirus type 12 in permissive and nonpermissive cells

The development of adenovirus type 12 T antigen and of the complex of antigenic early proteins designated as P antigen was studied by immunofluorescence in productively infected KB cells and abortively infected RK-13 cells. T antigen is detected in both cell types very early in infection. In KB cells it presents the well known pattern of nuclear dots and flecks but in RK-13 cells at the time of maximum abundance, 18 hours p.i., T antigen forms a net of long filaments that fills the nucleus. Later, part of the filaments condense into a large aggregate that finally is apparently degraded. P antigen in infected RK-13 cells looks like T antigen in KB cells. In these cells, besides an early phase wherein P antigen is almost indistinguishable from T antigen, a late component is evident under the form of large balls and rosettes. The possible identification of this component with the DNA binding protein is discussed.